Determining Optimum Bandwidth for Low Pass Bessel Filters and Other Filters

[Muhammad Khalid]

Hello fellow researchers,

I am currently working on a project that involves the use of low pass Bessel filters and other filters in OptiSystem 15. I am having difficulty determining the optimum bandwidth for these filters and was wondering if anyone has experience with this software and could provide some guidance on how to calculate the optimum bandwidth for these filters. Any help would be greatly appreciated.

Thank you in advance.

[Ahmad Atieh]

Dear Muhammad,
Typically, the BW is selected as 0.75 of the bit rate or baud rate depending on bits or symbol transmission. However, you may increase the filter BW to collect more signal, although more noise will be also included.
Regards,
Ahmad

[Ahmad Atieh]

Dear Muhammad,
Typically, the BW is selected as 0.75 of the bit rate or baud rate depending on bits or symbol transmission. However, you may increase the filter BW to collect more signal, although more noise will be also included.
Regards,
Ahmad

[Preston Jackey]

Dear Ahmad,

Thank you for your prompt reply and the helpful information. I appreciate your explanation on the typical selection of bandwidth as 0.75 of the bit rate or baud rate.
I just wanted to clarify that the 0.75 factor for bandwidth selection applies to all filters, such as Bessel and Butterworth, and will have the same value for bandwidth, correct?

Additionally, I was wondering if you could provide some guidance on how to use a spectrum analyzer to find the 3dB response and then calculate the optimal bandwidth.

Thank you again for your time and assistance.

Best regards,
Muhammad

[Preston Jackey]

Dear Ahmad,

Thank you for your prompt reply and the helpful information. I appreciate your explanation on the typical selection of bandwidth as 0.75 of the bit rate or baud rate.
I just wanted to clarify that the 0.75 factor for bandwidth selection applies to all filters, such as Bessel and Butterworth, and will have the same value for bandwidth, correct?

Additionally, I was wondering if you could provide some guidance on how to use a spectrum analyzer to find the 3dB response and then calculate the optimal bandwidth.

Thank you again for your time and assistance.

Best regards,
Muhammad

[Ahmad Atieh]

Dear Muhammad,
The 0.75 factor is a not carved in stone. You may change it around this value depending on the filter roll-off factor. You could always check the signal quality after the filter and decide.
Regards,
Ahmad

[Ahmad Atieh]

Dear Muhammad,
The 0.75 factor is a not carved in stone. You may change it around this value depending on the filter roll-off factor. You could always check the signal quality after the filter and decide.
Regards,
Ahmad

[Preston Jackey]

Dear Ahmad,

Can you explain the difference in bandwidth between low pass Bessel and Butterworth filters when cut-off frequency is set at 0.75*bit rate? How to calculate the optimum bandwidth and 3dB frequency response in Optisystem? Can you also provide the components required and the step-by-step procedure for this calculation?

[Preston Jackey]

Dear Ahmad,

Can you explain the difference in bandwidth between low pass Bessel and Butterworth filters when cut-off frequency is set at 0.75*bit rate? How to calculate the optimum bandwidth and 3dB frequency response in Optisystem? Can you also provide the components required and the step-by-step procedure for this calculation?

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